For example, Patent Literature 1 discloses an oil supply apparatus in which oil is introduced into a crank shaft from a specific crank journal among crank journals of the crank shaft and the oil is supplied to respective crank pins through an inside passage formed in the crank shaft. The oil supply apparatus is configured such that oil discharged from an oil pump is supplied to a crank bearing section which bears the specific crank journal (referred to as a specific crank journal) through a main oil path and, at the same time, oil is supplied to crank bearing sections which bear crank journals other than the specific crank journal through a branch oil path which branches from the main oil path. In addition, the oil supply apparatus is configured such that, by performing oil supply control with a flow rate control valve provided on the branch oil path and the like, oil supply amounts to the specific bearing section and to the other crank bearing sections are kept at appropriate amounts.
Generally, a required oil amount (required oil pressure) of oil differs depending on an operation state of an engine (rotational speed, load, oil temperature, and the like). This is due to the fact that oil amounts suitable for lubrication and cooling differ in accordance with the operation state of the engine and that activation and deactivation of hydraulic operating devices such as a variable valve timing mechanism must be switched depending on the operation state of the engine. In consideration thereof, according to Patent Literature 1 described above, a required oil amount (required oil pressure) of each crank bearing section can be appropriately secured by controlling the flow rate control valve provided on an oil path in accordance with the operation state of the engine.
However, as the required oil amount (required oil pressure) of oil changes in accordance with operation states of an engine, solely controlling a flow rate control valve often results in an oil pump operating in a wasteful manner as a whole and creating drive loss even if a required oil amount (required oil pressure) is satisfied. Therefore, there is room for improvement in this regard.